assume cs:code
code segment
start: 
       push cs
       pop ds

       mov ax,0
       mov es,ax
       mov si,offset int7c
       mov di,200h
       mov cx,offset int7cend-offset int7c
       cld
       rep movsb

       cli
       mov word ptr es:[7ch*4],200h
       mov word ptr es:[7ch*4+2],0
       sti

       mov ax,4c00h
       int 21h

int7c:
       push ax
       push bx
       push cx
       push dx
       push es

       push ax
       mov ax,dx
       mov dx,0
       mov cx,1440
       div cx
       mov dh,al
       mov ax,dx
       mov cl,18
       div cl
       mov ch,al
       add ah,1
       mov cl,ah
       mov dl,0
       pop ax
       mov al,1
       add ah,2
       int 13h

       pop es
       pop dx
       pop cx
       pop bx
       pop ax
       iret

int7cend:nop
code ends
end start
